<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div class="flex">
        <div class="top"></div>
        <div class="bottom"></div>
    </div>
</body>
<style>
    .flex{
        display: flex;
        height: 100%;
        width: 200px;
        background-color: aqua;
    }
</style>
</html>